1. Field of the Invention
This application is directed to coating systems for applying labels to polyolefin bottles and other containers. More particularly, this application is directed to heat-activatable labeling systems formed using solvent-based adhesives containing blends of ethylene-vinyl acetate polymer resins tackified with polyamides, polyesters, polyterpenes, terpene phenolics, acrylics, aliphatic hydrocarbon resins, hydrogenated rosins and/or rosin esters and preferably plasticized by solid plasticizers. Other components of the label include pigmented resin design layers and an abrasion resistant coating.
2. Description of the Related Art
Current heat-activatable adhesives used on heat transfer labels for application to polyethylene and polypropylene containers, having a surface energy of approximately 30 dynes/cm do not bond well to those surfaces unless the plastic surfaces are highly oxidized by either flame or electrical discharge treatment to a level of 35 dynes/cm or above, or alternatively, unless a surface coating or tie-coat is applied to the substrate. Such treatments add to the cost of the labeling process by incurring added energy or raw material costs, reducing labeling production speeds and exposure of the labeling plant to fire and explosion hazards.
Further deficiencies in known labeling systems are lack of hot molten tack, poor bond-ability to untreated or minimally-treated polyolefin surfaces resulting in poor and unreliable adhesion particularly when the labeled item is exposed to extreme temperature or humidity conditions. Pressure sensitive labels, tacky at room temperature and requiring use of a disposable release liner, also are used for application to polyolefin containers.